Fiber debonding during conversion



Dec. 12, 1967 J. R. coowm FIBER DEBONDING DURING CONVERSION Filed, July 13, 1964 United States Patent 3,357,059 FIBER DEBONDIN G DURING CONVERSION Joseph R. Godwin, Charlotte, NC, assignor to Celanese Corporation, a corporation of Delaware Filed July 13, 1964, Ser. No. 382,261 11 Claims. (Cl. 19-.3)

This invention relates to the art of debonding fibers during the conversion of tow to sliver, and more particularly to an improved apparatus and process for debonding fibers during said conversion wherein the tow comprises synthetic filaments such as cellulose triacetate or polyester. The term tow as used in the present specification and claims denotes a bundle of generally parallel continuous filaments containing at least about 500 filaments and having a total denier of at least about 1000. Preferably, the tow is crimped and, if crimped, preferably has a crimp frequency of from about 2 to 20 and most preferably from about 4 to 12 crimps/inch.

Their warmth, high covering power, and esthetic appeal have created a huge market for spun yarns. With the advent of synthetic yarns, which are conventionally produced in tow form, techniques for converting said tows to staple form were called for in order that spun synthetic yarns could be made expeditiously. Accordingly, methods and corresponding apparatuses were developed for converting tow into a continuous elongated body comprising staple; such continuous elongated bodies are commonly known as sliver or top and are generically referred to in the present specification and claims as sliver.

Synthetic filament tow oftentimes is maintained as a coherent unit to aid in handling and processing of the tow during its manufacture, during subsequent conversion of the tow to sliver, and during manufacture of spun yarn from said sliver; this generally is accomplished by crimping the yarn prior to packaging thereof. However, said crimping compresses adjacent filaments of the tow into the same configuration and causes many of said adjacent filaments mutually to adhere; the filaments so adhered are referred to as being married and each area of the yarn where such condition exists is referred to as a Shiner. Often, shiners will interfere in the processes of converting the tow to sliver and the sliver to spun yarn and result in poor sliver and spun yarn due to the presence of married filaments in the sliver. Furthermore, during stages of the sliver making and spinning operations, the adjacent filaments and fibers cut therefrom are placed under compression which creates further marriages.

Among the processes and apparatuses which have been evolved for converting tow to sliver in a class of .processes and apparatuses which, broadly, involve the feeding of a flat sheet of tow suitably tensioned to a cutter, the shearing by the cutter of the band of tow at an acute angle without disturbing the parallel arrangements of the constituent filaments thereby to form staple and the redistribution of fiber ends to give a stable, continuous product in the form of a sliver; this class is typified by the operation of the commercially well known Pacific Converter. The present invention will be described in relation to the Pacific Converter but it will be understood by those skilled in the art that the present invention is broadly applicable to the entire class of apparatuses and processes which the Pacific Converter and its mode of operation typify. A conventional Pacific Converter and its mode of operation is described in detail in another commonly assigned U.S. patent application Ser. No. 382,262, filed July 13, 1964 entitled, Ball Warping and Converting Opened Tow, to G. A. Watson, J. R. Williams and J. A. Godwin, especially in the description of FIG. 2 of said application; said detailed description is hereby incorporated by reference into the present speciice fication. Also incorporated by reference into the present specification is the description of the same conventional Pacific Converter and its operation appearing in Modern Yarn Production, edited by G. R. Wray and published in 1960 by Columbine Press Company Limited, Manchester, England, especially at p. 61, line 13 to p. 69, line 3 thereof.

Although the Pacific Converter has produced generally satisfactory results in the processing of many synthetic filaments and blends of such synthetic filaments with wools and cottons, it has heretofore been generally impossible to employ this apparatus to obtain a staple product of good uniformity in the processing of cellulose triacetate (i.e., substantially fully esterified cellulose, containing fewer than 0.29 free hydroxyl groups per anhydroglucose unit), and in connection with many polyesters such as polyethylene terephthalate; this difficulty apparently has been due to severe bonding or fusing (marrying) of fibers at points Where they have been cut by the Pacific Converter, a substantial amount of which is not removed by the debonding action of the converter.

To a generally lesser extent, essentially the same problem has been encountered in the conversion of other synthetic filament tows. Thus, oftentimes it is found that the sliver obtained from the Pacific Converter is rather non-uniform. This is due to the fact that the initial tows often contain shiners all of which are not removed by the debonding action of the converter and, furthermore, the fusing effect due to cutting, noted above, generally exists to some extent with all synthetic filament tows.

Due to this inadequacy of the Pacific Converter, the economic advantages to 'be gained by the utilization of the synthetics in combination with wool, cotton or other natural fibers has substantially been mitigated by the increased cost of processing arising due to the required abnormally extensive utilization of picking, carding, gilling, combing, and the like equipment in order to obtain necessary fiber separation.

A further deficiency of the Pacific Converter has been that it has not been possible to produce staple therewith having an average staple length of less than about 3" while maintaining an acceptable degree of uniformity (i.e., freedom from irregularities such as neps and shiners or married filaments) in the staple product. The cotton system can spin sliver having a staple length as low as about /2 or inch but not more than about 2% inches. The worsted system cannot spin sliver having a staple length of less than about 3 inches. Thus, in the past it has not been possible to produce sliver on the Pacific Converter suitable for cotton system spinning; since there is a great deal of cotton system spinning machinery in existence, this clearly has been a significant shortcoming of the Pacific Conveter. The present invention remedies this shortcoming; it has now been found that a Pacific Converter provided with the improved debonding rolls according to the present invention will yield acceptable sliver of a staple length as low as about 1 /2 inches or less, suitable for cotton system spinning.

It is accordingly among the objects of this invention to provide a process and apparatus for implementing the debonding of filamentary materials, especially cellulose tri acetate and polyesters, e.g. polyethylene terephthalate, during their conversion from continuous filament to staple.

A further object of the invention is to provide improved debonding rolls for the Pacific Converter.

It is also an object of the invention to provide novel means for making it possible to produce synthetic/natural fiber blends at competitive processing costs.

These and other objects and advantages of the invention which will become hereafter apparent are achieved by advancing the cut filaments (i.e., staple fibers) in a path permitting some out filaments to be contacted and gripped while they are moved. Those fibers of said staple which have not previously been gripped are then grippingly engaged whereby there will be relative longitudinal movement between the fibers and thus they are separated and any crimp in them is deregistered. This mode of staple treatment is most readily accomplished by modifying the Pacific Converter to replace the debonding and shearing rolls by two separated roll pairs, one roll of each pair being threaded helically, and the other formed with a resilient surface. It is preferred that the spacing between the pairs of debonding rolls is such that each end of a group of staple fibers which have been bonded together, as for example by the cutting operation, are nipped by one or the other pair of rolls. The helical threading is flattened at its apex to provide a land defining a fiber gripping portion, while the valleys between threads define a fiber passing portion. The difference in distance between the land and its axis of rotation and the valley and its axis of rotation produce a speed differential providing a mechanical draft on the fibers so that the selective positive nipping of fibers between the top lands of the threads on the threaded roll and the elastically covered companion roll produces a thorough debonding of the individual fibers within each bundle.

The combination of helically threaded and resilient surfaced rolls just described is typical of a general type of apparatus for deregistering (opening) crimped tow which apparatus employs one or more profiled or patterned rolls as described for example in U.S. Patents Nos. 3,032,829 and 3,103,220 and Canadian Patent No. 674,101 (corresponding to a copending U.S. patent application Ser. No. 151,900, filed Nov. 13, 1961, now U.S. Patent No. 3,156,016, in the names of D. T. Dunlap and R. E. St. Pierre); any such apparatus may be used in the present invention.

A feature of the invention resides in the arrangement of the profiled or patterned roll appartus so that it acts to simultaneously draft and debond the fibers.

Another feature of the invention resides in the use of simply fabricated pairs of debonding rolls (e.g., two pairs), one roll of each pair being helically grooved so that some of the fibers to be debonded are gripped between the first pair of rolls (feed rolls) while an adjacent fiber group is gripped between thesecond pair of rolls (ratio rolls) and simultaneously moved faster and longitudinally displaced with respect to the first gripped fibers, thus effecting desired separation and debonding of the fibers. The ratio of the speed of the ratio rolls to the speed of the feed rolls determines the degree to which the fibers are debonded. Generally: considerable debonding occurs at a ratio of from about 1.1:1 to about 2.0:1 and maximum debonding occurs at a ratio of from about 1.2:1 to about 1.8: 1, depending on the nature of the tow.

The specific details of a preferred embodiment of the invention will be made manifest and particularly pointed out in clear, concise and exact terms in conjunction with the accompanying drawings wherein:

FIG. 1 is a top plan view schematically showing a portion of a converter and the relationship between the novel debonding rolls and the cutter of the converter; and

FIG. 2 is a schematic elevational view of the debonding rolls and cutter shown in plan in FIG. 1, with the tow to be processed shown trained between the rolls; and

FIG. 3 is a schematic detail of a portion of the staple fibers during conversion and the nip sections of the debonding roll pairs, illustrating how the fibers are separated by the debonding action of the rolls; and

FIG. 4 is an elevational view of the rolls of a debonding roll pair.

Referring now more particularly to the drawings, like numerals in the various figures will be employed to designate like parts.

As shown schematically, in FIGS. 1 and 2, the fracturing roll of a Pacific Converter, is arranged to receive the tow T. The cutter comprises cutting roll 10 and anvil roll 11 which rolls cooperate to cut the continuous filaments of which tow T is comprised. Spaced downstream from the cutter are a first pair of debonding rolls 12. One roll 15 of this pair 12 is formed with a helically threaded surface 16. Roll 15, which is here shown as the upper roll of the pair, is formed of steel, or the like material subject to being machined or otherwise fabricated with the requisite helical surface.

In a preferred arrangement where a conventional Pacific Converter has been provided with the debonding rolls of the present invention, the threaded roll is machined from cylindrical stock with a length of between 25 and 30 inches, and provided with a central threaded area between 12 and 16 inches in length and a diameter of between 1.75 inches and 2.25 inches, with 12 threads per inch, having a throat depth between .04 and .06", with each thread formed with a land 17( see FIG. 4) between .015" and .02". The diameter of the stock remote from the threaded area is preferably less than the diameter of the threaded area.

Mating with threaded roll 15 of roll pair 12 is a cushioning roll 20 having a resilient surface 21 which is preferably formed by covering a steel roll shaft with rubber. In a preferred installation, the rubber, or otherwise cushioned surface, is made to extend over a length greater than that of the extent of the mating threaded roll. Thus for mating with roll 15 as shown in FIG. 4, a cushioning roll 20 is formed with a cushioning surface 21, twenty inches in axial length, and having a diameter of one inch.

A second roll pair 25 is arranged at a spaced distance from the first roll pair along the tow path. This distance is preferably slightly less than the fiber lengths, so as to insure nipping between the ends of the fibers. Debonding roll pair 25 is formed like first debonding roll pair 12 of substantially the same material and with substantially the same dimensions as heretofore given. Thus, roll 22 has a helically threaded surface 23 and roll 24 is constructed like roll 20. The lands of the flattened helical threads cooperate with the cushioned surface to form a fiber gripping portion or zone while the troughs or valleys between lands form a fiber passing zone as in the case with first debonding roll pair 12.

Operation In use, the aforedescribed debonding roll pairs 12 and 25 are arranged to receive the cut tow T (i.e., staple) from the cutter of the converter. The tow after cutting is here referred to as staple. The staple is passed between the helically threaded roll and the cushioning roll of each pair. As best seen in FIG. 3, some of the fibers of the staple are gripped between the lands on the helical roll and the cushioning roll of the roll pair, while others of the fibers are passed in the helix troughs or valleys.

Where the second roll pair is driven at a greater r.p.m. than the first roll pair and each roll pair is formed with rolls of equal diameter, it is apparent that the fibers engaged at the land of the helical threads will be moved relative to those fibers lying in the trough. As shown in FIG. 3, where a fiber is passed at the trough by the second pair of rolls, it will be gripped at the land by the first pair. Thus the fibers labeled a are firmly held between the lands of the thread and the cushioning roll in the first nip section and are not held in the second nip; while the fibers labeled [1 are held firmly between the top lands of the threads and the cushioned surface of the second roll pair. As a result of this fiber gripping, those fibers labeled a will be moved longitudinally relatively to those labeled b.

The above described structural arrangement has been found particularly useful in effecting the conversion of cellulose triacetate and polyester, especially polyethylene terephthalate, tows on Pacific Converters to yield a staple product which is readily blendable with wool or cotton and the like.

The tows of synthetic filaments in accordance with the present invention may comprise organic derivatives of cellulose such as the esters or others thereof, for example cellulose organic acid esters such as cellulose acetate, cellulose propionate, cellulose butyrate, cellulose bonzorate, cellulose acetate formate, cellulose acetate pro ionate, cellulose acetate butyrate, and the like, ethers such as ethyl cellulose, etc. The esters may be ripened and acetonesoluble, such as conventional cellulose acetate, or may be substantially fully esterified, i.e., contain fewer than 0.29 free hydroxyl groups per anhydroglucose unit, e.g. cellulose triacetate. The tows of synthetic filaments according to the present invention also include regenerated cellulose, such as viscose rayon or cuprammonium rayon, and chemically modified or cross-linked regenerated cellulose.

The tows of synthetic filaments according to the present invention further include thermoplastic or solvent-soluble or -dispersible polymeric materials such as superpolyamides, e.g., nylon, super-polyesters such as polyethylene terephthalate, polyglycolic acid and copolymers thereof, acrylonitrile polymers and copolymers, polymers and copolymers of olefins and vinyl esters such as ethylene, propylene, vinyl chloride, vinyl acetate, vinylidene chloride, vinylidene cyanide, and the like.

In the aforesaid other U.S. patent application, entitled Ball Warping and Converting Opened Tow, to G. A. Watson, J. R. Williams and J. A. Godwin, filed on the same date as this application, there is disclosed the preprocessing of tow by means of profiled or patterned rolls in order to improve processability thereof in the Pacific Converter. It is to be understood that said pre-processing may be used in combination with the present invention in order to obtain sliver of the same character and quality.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of my invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Means for converting a tow to sliver, said means comprising: cutter means mounted to move with the tow in pressure applying relationship with respect thereto; anvil means arranged in opposed relationship with respect to said cutter means so that the tow will be contacted on opposed sides between said cutter means and said anvil means, said cutter means mounted to exert a pressure along a diagonal with respect to the path of movement of the tow and to cooperate with said anvil means to out said tow into staple fibers; and two pairs of relatively spaced debonding rolls, at least one roll of each pair having a resilient surface, and the other roll of each pair having a helically threaded portion and being mounted so that said helically threaded portion will contact some of said fibers.

2. In apparatus for converting tow to sliver, said apparatus having means for cutting the tow into staple fibers of desired length, means for debonding the fibers, said debonding means comprising: a first helically threaded roll; a cushioning roll against which said helically threaded roll bears; a second helically threaded roll; and a second cushioning roll against which said second threaded roll bears, said second helically threaded roll being a receiver for said staple fibers passed through said first helically threaded roll.

3. Apparatus as in claim 2 in which each said helically 6 threaded roll comprises a helical thread having flat lands which abut the cushioning roll.

4. Apparatus as in claim 2 in which said first threaded roll and cushioning roll are spaced from said second threaded roll and cushioning roll by a distance less than the average length of the staple fibers forming the sliver.

5. A method for converting tow into a sliver, said method comprising the step-s of: longitudinally advancing tow; contacting said tow at spaced points with sufiicient pressure to sever the tow at the points of contact to form staple fibers; advancing the fibers; engaging some of the fibers at an angle relative to the direction of advance of said staple fibers in at least two fiber engaging zones; longitudinally displacing the engaged fibers with respect to the nonengaged fibers and subsequently forming a sliver from said staple.

6. The method of claim 5 wherein at least some of said nonengaged fibers not contacted in said engaging ZOIIGS are engaged at points remote from said fiber engagmg zones.

7. The method of claim 5 wherein the engaged fibers are moved at a speed greater than the nonengaged fibers.

8. The method of claim 5 wherein the fibers are gripped by exerting a pressure against one side of the fibers while cushioning the other side thereof.

9. In a converter in which tow is formed into staple fibers and then said stable fibers are formed into a sliver, said converter comprising a stapling means and debonding means, wherein tow is passed from said stapling means to said debonding means as staple fibers prior to forming said staple fibers into said sliver, said debonding means comprising: a plurality of fiber engaging members in spaced relationship to each other, said engaging members being in pressure communication with a fiber supporting means and said spaced relationship of said fiber engaging members forming fiber passages wherein said engaging members :grip at least some of the fibers as the fibers are moved longitudinally to a second plurality of fiber engaging members, said second plurality of engaging members being in spaced relationship to each other and in pressure communication with a fiber supporting means Wherein said spaced relationship of said fiber engaging members form fiber passages, wherein said second engaging members grip at least some of said fibers passing said first plurality of fiber engaging members, thereby moving at least some of said fibers longitudinally relative to each other to debond same, wherein at least one of said plurality of engaging members is inclined at an angle relative to the direction of advance of said staple fiber.

10. The converter of claim 9 wherein said fiber supporting means are formed by cushioning means.

11. The converter of claim 10 wherein said plurality of fiber engaging members comprise a helically threaded roll and said cushioning means comprising a resilient surfaced roll against which said threaded roll bears as said rolls are rotated.

References Cited UNITED STATES PATENTS 2,232,348 2/ 1941 Svoboda 19.5 1 2,417,599 3/1947 Joyce 19-65 2,438,469 3/ 1947 Wilkie 19-51 3,156,016 11/1964 Dunlap et al 19-65 XR MERVIN STEIN, Primary Examiner.

D. NEWTON, Assistant Examiner. 

1. MEANS FOR CONVERTING A TOW TO SLIVER, SAID MEANS COMPRISING: CUTTER MEANS MOUNTED TO MOVE WITH THE TOW IN PRESSURE APPLYING RELATIONSHIP WITH RESPECT THERETO; ANVIL MEANS ARRANGED IN OPPOSED RELATIONSHIP WITH RESPECT TO SAID CUTTER MEANS SO THAT THE TOW WILL BE CONTACTED ON OPPOSED SIDES BETWEEN SAID CUTTER MEANS AND SAID ANVIL MEANS, SAID CUTTER MEANS MOUNTED TO EXERT A PRESSURE ALONG A DIAGONAL WITH RESPECT TO THE PATH OF MOVEMENT OF THE TOW AND TO COOPERATE WITH SAID ANVIL MEANS TO CUT SAID TOW INTO STAPLE FIBERS; AND TWO PAIRS OF RELATIVELY SPACED DEBONDING ROLLS, AT LEAST ONE ROLL OF EACH PAIR HAVING A RESILIENT SURFACE, AND THE OTHER ROLL OF EACH PAIR HAVING A HELICALLY THREADED PORTION AND BEING MOUNTED SO THAT SAID HELICALLY TREADED PORTION WILL CONTACT SOME OF SAID FIBERS. 